This invention relates to a device for providing an acoustic signal to a patient when a predetermined load is placed on the patient's foot.
Devices of the above kind are used for warning the patient in those cases where due to a fracture of a leg or other orthopedic surgery operations the load on the leg as related to the patient's weight must be limited. With respect to the therapy of less complicated leg fractures an initial load on the patient's foot of only about 20 kg is considered as an allowable limit when the patient will start with his first attempts to walk after an operation of his fractured leg whereby such a lowermost load will then subsequently be increased stepwise to thereby secure a correct healing or recovery of the operated leg.
A prior art device as described in U.S. Pat. No. 3,974,491 comprises a resilient foot pad adapted to overlie the inner sole of a shoe and having a core for example of a foamed plastic which receives a resilient tube being filled with a liquid and extending from adjacent the toe end of the pad to adjacent its heel end with a plurality of loops. The tube of the foot pad is connected via a tube connector to a resilient bladder which serves as a pressure responsive means communicating with the liquid. The bladder is to actuate a signaling means at a predetermined pressure of the liquid via a pivotally mounted bell crank lever that engages a control button of a switch which in turn actuates a battery driven buzzer. All of these means are housed within a box which by means of a loop band having a hook and loop fastener may be mounted on the patient's leg. Whenever a buzzer signal is supplied the patient will thusly be warned on having reached a predetermined load on his foot which by means of a compression coil spring biasing the bell crank lever against the bladder may be adjusted within a predetermined range between a still allowable lowermost load on the patient's foot and increasing higher load values.
Since with such known devices the signaling means comprises electrical means such as a switch and a battery driven buzzer as well as interconnecting wires it is quite apparent that thereby the costs for producing the device and those for maintaining the service of such devices are high whereby also the operation of these devices may as well not be considered as perfectly reliable.